This invention relates to sulfurized olefins and, in particular, to polysulfurized olefins used in lubricating oil compositions and to a method for preparing same.
Sulfurized olefins are used in lubricants such as crankcase oil and gear lubricants to provide extreme pressure properties.
Papay et al, U.S. Pat. No. 4,204,969 describes such a product in which sulfur monochloride is reacted with an aliphatic monoolefin to obtain an intermediate which is reacted with sulfur and sodium sulfide.
One problem in the field of sulfurized olefin additives used for improving the extreme pressure properties of lubricants continues to be the development of a sulfurized polyolefin additive which is sufficiently soluble in both mineral oils and synthetic oils (particularly those of the polyalphaolefin type) to be usable as extreme pressure additives.
This problem is addressed in Born et al, U.S. Pat. No. 4,645,610 which teaches that the solubility of such olefin polysulfide additives in both mineral and synthetic oils is inversely proportional to the sulfur content of the additive. That is, as the sulfur content of the additive increases the solubility of the additive in both mineral and synthetic oils (particularly those of the polyalphaolefin type) decreases. Reportedly, olefin polysulfide additives of high sulfur content having enhanced solubility in both mineral and synthetic oils can be obtained according to Born et al by contacting an addition product produced by the reaction of at least one aliphatic monoolefin containing 2 to 5 carbon atoms and sulfur monochloride or dichloride with a hydrocarbyl halide and at least one sulfur compound selected from sulfides, hydrosulfides and polysulfides of alkali metals, ammonium or alkaline-earth metals and usually elemental sulfur in an aqueous or aqueous alcoholic medium at certain reaction conditions.
Griffin et al, U.S. Pat. No. 4,563,302 also reports that sulfurized olefins having improved solubility in lubricating oils (especially in alpha-olefin oligomer synthetic oils) can be obtained by reacting an alkyl mercaptan, sulfur, sodium sulfide and, optionally, sodium hydrosulfide in an aqueous alcohol medium with an adduct prepared by reacting a monoolefin with sulfur monochloride or sulfur dichloride.